Multipurpose test equipment input circuitry
AssigneeMotorola, Inc.
InventorsJames E. Olivenbaum, Robert H. Bickley
Life of this patent
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Abstract
An input terminal adapted to receive 0 to 300 volts AC or DC is connected through AC or DC connecting circuits, coupled into the path by switches, and attenuating apparatus including a plurality of ranges automatically switched into the path in response to the amplitude of an input signal, to a buffer which includes overvoltage protection and provides a relatively high input impedance with a relatively low output or source impedance. A frequency counter is connected through a hysteresis amplifier, a digital volt meter is connected through an amplifier including 60 cycle filtering and an oscilloscope is connected through an independent gain amplifier to the output of the buffer.
Claims8
Multipurpose test equipment input circuitry comprising:
- (a) input means including a single input terminal for receiving AC and DC signals;
- (b) switching means connected to said input means for selecting one of an AC and DC coupling circuit;
- (c) attenuation means connected to said coupling circuits for receiving input signals from said input means and attenuating the amplitude of the input signals to at least a predetermined value;
- (d) buffer means connected to said attenuation means for providing a relatively high input impedance at said input means and a relatively low source impedance for circuitry attached to an output thereof, and including circuitry for preventing damage to said buffer means upon the application of greater than a predetermined amplitude of signal to said buffer means, said buffer means including first field effect transistor means providing the relatively high input impedance with current limiting resistance in series with an input gate thereof to provide protection against overloads of a first polarity and second junction field effect transistor means connected as a diode to the input gate to provide protection against overloads of a second polarity;
- and
- (e) a plurality of circuits connected to the output of said buffer means, each of said circuits providing signals for a different function of multipurpose test equipment in response to the application of signals from said buffer means.
Dependencies are inferred from the claim text.